package com.atguigu.practice;

import java.util.Scanner;

public class ChampagneTower {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        int poured=scanner.nextInt();
        int query_row=scanner.nextInt();
        int query_glass=scanner.nextInt();
        double tower[] = new double[]{(double) poured};
        for (int i = 1; i <= query_row; i++) {
            double[] arr = new double[i + 1];
            for (int j = 0; j < i; j++) {
                double v = tower[j];
                if (v > 1) {
                    arr[j] += (v - 1) / 2;
                    arr[j + 1] += (v - 1) / 2;
                }
            }
            tower = arr;
        }
        System.out.println(Math.min(1,tower[query_glass]));
    }
}
